I have a client who has finished signing up for a VPP ID, is able to log in to the VPP store with that ID, but App Store Connect is rejecting it with the message:
The apple ID you entered, ***@***.org, was not created for use with the Volume Purchase Program. To learn more about how your customers can sign up for the Volume Purchase Program, visit http://enroll.vpp.itunes.apple.com.
Going to that link is useless--that's just the enrollment/log in page, and he's already enrolled and able to log in.
I've had nothing but trouble with VPP since the recent changes, with VPP IDs and DEP IDs being rejected only to suddenly be approved, and clients having difficult times getting VPP IDs in the first place. I'm very frustrated with it.